Emulsion flow optimization method for suppressing vibration of cold continuous rolling mill

ABSTRACT

An emulsion flow optimization method suitable for a cold continuous rolling mill that aims to achieve vibration suppression. The method aims to suppress vibrations by an oil film thickness model and a friction coefficient model. An optimum set value of the emulsion flow rate for each rolling stand that aims to achieve vibration suppression is optimized on the basis of an over-lubrication film thickness critical value and an under-lubrication film thickness critical value that are proposed. The method greatly reduces the incidence of rolling mill vibration defects, improves production efficiency and product quality, treats rolling mill vibration defects, and improves the surface quality and rolling process stability of a finished strip of a cold continuous rolling mill.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 U.S. National Phase of PCT International Application No. PCT/CN2019/097396 filed on Jul. 24, 2019, which claims benefit and priority to Chinese patent application no. 201810818600.7 filed on Jul. 24, 2018, contents of both are incorporated by reference herein in their entireties.

TECHNICAL FIELD

The invention relates to the technical field of cold continuous rolling, in particular to an emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill.

BACKGROUND

Rolling mill vibration defect is always one of the difficult problems that perplex the high-speed and stable production of an on-site cold continuous rolling mill and ensure the surface quality of finished strip. In the past, on-site treatment of rolling mill vibration defects generally depends on the control over the speed of the rolling mill, by which the vibration defects can be weakened, but the improvement of production efficiency is restricted and the economic benefits of enterprises are seriously affected. However, for the cold continuous rolling mill, its device and process features determine the potential of vibration suppression. Therefore, setting reasonable process parameters is the core means for vibration suppression. Through theoretical research and on-the-spot tracking, it is found that the rolling mill vibration is directly related to the lubrication state between the roll gaps. If the roll gaps are in an over-lubrication state, it is indicated that the friction coefficient is too small, thus it is likely to cause slip in the rolling process to cause the self-excited vibration of the rolling mill; if the roll gap is in an under-lubrication state, it is indicated that the average oil film thickness between the roll gaps is less than the required minimum value, thus it is likely to cause sharp increase of the friction coefficient due to rupture of oil films in the roll gaps during the rolling process, which leads to the change of rolling pressure and periodic fluctuation of system stiffness, and thus also causes self-excited vibration of the rolling mill. It can be seen that the key to suppress the vibration of the rolling mill is to control the lubrication state between the roll gaps. On the premise that the rolling schedule, the rolling process and process parameters such as the emulsion concentration and the initial temperature are determined, the setting of emulsion flow rate directly determines the roll gap lubrication state of each rolling stand of the cold continuous rolling mill, and is the main process control means of the cold continuous rolling mill.

The patent No. 201410522168.9 discloses a cold continuous rolling mill vibration suppression method, which comprises the following steps: 1) arranging a cold rolling mill vibration monitoring device on the fifth or fourth rolling stand of the cold continuous rolling mill, and determining whether the rolling mill is about to vibrate by the energy of a vibration signal; 2) arranging a liquid injection device which can independently adjust the flow rate in front of an inlet emulsion injection beam of the fifth or fourth rolling stand of the cold rolling mill; and 3) calculating the forward slip value to determine whether to turn on/off the liquid injection device. The patent No. 201410522168.9 discloses a comprehensive emulsion flow optimization method for ultra-thin strip rolling of a cold continuous rolling mill. The existing device parameters and process parameter data of a cold continuous rolling mill control system are used to define the process parameters of comprehensive emulsion flow optimization considering the slip, vibration and hot slide injury as well as shape and pressure control, and determine the optimal flow rate distribution value of each rolling stand under the current tension schedule and rolling reduction schedule. The comprehensive optimization setting of emulsion flow rate for ultra-thin strip rolling is realized by computer program control. The above patents mainly focus on monitoring equipment, forward slip calculation model, emulsion flow rate control and other aspects to realize rolling mill vibration control; vibration is only a constraint condition of emulsion flow rate control, and is not the main treatment object.

SUMMARY (I) Technical Problems Solved

The purpose of the invention is to provide an emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill. The method aims to suppress vibrations, and by means of an oil film thickness model and a friction coefficient model, comprehensive optimization setting for the emulsion flow rate for each rolling stand is realized on the basis of an over-lubrication film thickness critical value and an under-lubrication film thickness critical value that are proposed so as to achieve the goals of treating rolling mill vibration defects, and improving the surface quality of a finished strip.

(II) Technical Solution

An emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill includes the following steps:

-   -   S1, collecting device feature parameters of the cold continuous         rolling mill, wherein the device feature parameters include: the         radius R_(i) of a working roll of each rolling stand, the         surface linear velocity v_(ri) of a roll of each rolling stand,         the original roughness Ra_(ir0) of a working roll of each         rolling stand, the roughness attenuation coefficient B_(L) of a         working roll, the distance l between rolling stands, and the         rolling kilometer L_(i) after roll change of a working roll of         each rolling stand, wherein i is 1, 2, . . . , n, and represents         for the ordinal number of rolling stands of the cold continuous         rolling mill, and n is the total number of rolling stands;     -   S2, collecting key rolling process parameters of a strip,         wherein the key rolling process parameters include: the inlet         thickness h_(0i) of each rolling stand, the outlet thickness         h_(1i) of each rolling stand, strip width B, the inlet speed         v_(0i) of each rolling stand, the outlet speed v_(1i) of each         rolling stand, the inlet temperature T₁ ^(r), strip deformation         resistance K_(i) of each rolling stand, rolling pressure P_(i)         of each rolling stand, back tension T_(0i) of each rolling         stand, front tension T_(1i) of each rolling stand, emulsion         concentration influence coefficient k_(c), pressure-viscosity         coefficient θ of a lubricant, strip density ρ, specific heat         capacity S of a strip, emulsion concentration C, emulsion         temperature T_(c) and thermal-work equivalent J;     -   S3, defining process parameters involved in the process of         emulsion flow optimization, wherein the process parameters         include that an over-lubrication film thickness critical value         of each rolling stand is ξ_(i) ⁺ and the friction coefficient at         this time is u_(i) ⁺, an under-lubrication film thickness         critical value is ξ_(i) ⁺ and the friction coefficient at this         time is u_(i) ⁻, the rolling reduction amount is         Δh_(i)=h_(0i)−h_(1i), the rolling reduction rate is

${\varepsilon_{i} = \frac{\Delta h_{i}}{h_{0i}}},$ and the inlet temperature of each rolling stand is T_(i) ^(r), the distance l between the rolling stands is evenly divided into m sections, and the temperature in the sections is represented by T_(i,j) (wherein, 1≤j≤m), and T_(i) ^(r)=T_(i−1,m), the over-lubrication judgment coefficient is A⁺, and the under-lubrication judgment coefficient is A⁻;

-   -   S4, setting the initial set value of an emulsion flow rate         comprehensive optimization objective function of the cold         continuous rolling mill that aims to achieve vibration         suppression as F₀=1.0×10¹⁰;         wherein the executing order of steps S1 to S4 is not limited.     -   S5, calculating the bite angle α_(i) of each rolling stand         according to the rolling theory, wherein the calculation formula         is as follows:

${\alpha_{i} = \sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}},R_{i}^{\prime}$ is the flattening radius of the working roll of the i^(th) rolling stand, and is the calculation process value of rolling pressure;

-   -   S6, calculating the vibration determination index reference         value ξ_(0i) of each rolling stand;     -   S7, setting the emulsion flow rate w_(i) of each rolling stand;     -   S8, calculating the strip outlet temperature T_(i) of each         rolling stand;     -   S9, calculating an emulsion flow rate comprehensive optimization         objective function F(X):

$\left\{ {\begin{matrix} {{F(X)} = {{\frac{\lambda}{n}{\sum\limits_{i = 1}^{n}\sqrt{\left( {\xi_{i} - \xi_{0i}} \right)^{2}}}} + {\left( {1 - \lambda} \right)\max{❘{\xi_{i} - \xi_{0i}}❘}}}} \\ {\xi_{i}^{-} < \xi_{i} < \xi_{i}^{+}} \end{matrix};} \right.$

-   -   S10, determination whether the in-equation F(X)<F₀ is         established, if yes, enabling w_(i) ^(y)=w_(i), F₀=F(X), and         then turning to step S11, since F₀=1.0×10¹⁰ under the initial         circumstance, the value is very large, in the first calculation         process, F(X) must be smaller than F₀, and in the subsequent x         calculation processes, the corresponding F(X) is obtained with         the change of w_(i), and the x^(th) F₀ is the x−1^(th) F(X), if         the x^(th) F(X) is smaller than the x−1^(th) F(X), it is         determined that F(X)<F₀ is established and turn to step S11;         otherwise, turning directly to step S11;     -   S11, determining whether the emulsion flow rate w_(i) exceeds a         feasible region range, if yes, turning to step S12; otherwise,         turning to step S7, wherein the feasible region of w_(i) ranges         from 0 to the maximum emulsion flow rate value allowed by the         rolling mill.     -   S12, outputting an optimal emulsion flow rate set value w_(i)         ^(y), wherein w_(i) ^(y) is the value of w_(i) when the         calculated value of F(X) in the feasible region is minimum.

According to an embodiment of the present invention, the step S6 includes the following steps:

-   -   S6.1, calculating the neutral angle γ_(i) of each rolling stand:

${\gamma_{i} = {\frac{1}{2}{\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}\left\lbrack {1 + {\frac{1}{2u_{i}}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}} \right\rbrack}}};$

-   -   S6.2, calculating to obtain

$u_{i}^{+} = {\frac{1}{2\left( {{2A^{+}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = A^{+}},$ the roll gap is just in an over-lubrication state;

-   -   S6.3, calculating an over-lubrication film thickness critical         value ξ_(i) ⁺ of each rolling stand according to the         relationship formula between the friction coefficient and the         oil film thickness, namely u_(i)=a_(i)+b_(i)·e^(B) ^(·ξ) ^(i)         (in the formula, a_(i) is the liquid friction influence         coefficient, b_(i) is the dry friction influence coefficient,         and B_(i) is the friction coefficient attenuation index),         wherein

${\xi_{i}^{+} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{+} - a_{i}}{b_{i}}}};$

-   -   S6.4, calculating to obtain

$u_{i}^{-} = {\frac{1}{2\left( {{2A^{-}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = A^{-}},$ the roll gap is just in an under-lubrication state;

-   -   S6.5, calculating an under-lubrication film thickness critical         value ξ_(i) ⁻ of each rolling stand according to the         relationship formula between the friction coefficient and the         oil film thickness, namely u_(i)=a_(i)+b_(i)·e^(B) ^(·ξ) ^(i) ,         wherein

${\xi_{i}^{-} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{-} - a_{i}}{b_{i}}}};$ and

-   -   S6.6, calculating the vibration determination index reference         value ξ_(0i) of each rolling stand, wherein

$\xi_{0i} = {\frac{\xi_{i}^{+} + \xi_{i}^{-}}{2}.}$

According to an embodiment of the present invention, the step S8 includes the following steps:

-   -   S8.1, calculating the outlet temperature T₁ of the first rolling         stand, wherein

${T_{1} = {T_{1}^{r} + {\frac{1 - \left( {\varepsilon_{1}/4} \right)}{1 - \left( {\varepsilon_{1}/2} \right)} \cdot \frac{K_{1}{\ln\left( \frac{1}{1 - \varepsilon_{1}} \right)}}{\rho{SJ}}}}};$

-   -   S8.2, enabling i=1;     -   S8.3, calculating the temperature T_(i,1) of the first section         of strip behind the outlet of the i^(th) rolling stand, i.e.         T_(i,1)=T_(i);     -   S8.4, enabling j=2;     -   S8.5, showing the relationship between the temperature of the         j^(th) section and the temperature of the j−1^(th) section by         the following equation:

${T_{i,j} = {{{- \frac{2k_{0}w_{i}^{0.264}{\exp\left( {9.45 - {0.1918C}} \right)} \times 1.163l}{v_{1i}h_{1i}\rho{Sm}}}{T_{i,{j - 1}}^{- 0.213}\left( {T_{i,{j - 1}} - T_{c}} \right)}} + T_{i,{j - 1}}}},$ wherein k₀ is the influence coefficient of the nozzle shape and spraying angle, and 0.8<k₀<1.2;

-   -   S8.6, determining whether the in-equation j<m is established, if         yes, enabling j=j+1, and then turning to step S8.5; otherwise,         turning to step S8.7;     -   S8.7, obtaining the temperature T_(i,m) of the m^(th) section by         iterative calculation;     -   S8.8, calculating the inlet temperature T_(i+1) ^(r) of the         i+1^(th) rolling stand: T₁₊₁ ^(r)=T_(i,m);     -   S8.9, calculating the outlet temperature T_(i+1) of the         i+1^(the) rolling stand, wherein

${T_{i + 1} = {T_{i + 1}^{r} + {\frac{1 - \left( {\varepsilon_{i + 1}/4} \right)}{1 - \left( {\varepsilon_{i + 1}/2} \right)} \cdot \frac{K_{i + 1}{\ln\left( \frac{1}{1 - \varepsilon_{i + 1}} \right)}}{\rho{SJ}}}}};$

-   -   S8.10, determining whether the in-equation i<n is established,         if yes, enabling i=i+1, and then turning to step S8.3;         otherwise, turning to step S8.11; and S8.11, obtaining the         outlet temperature T_(i) of each rolling stand.

According to an embodiment of the present invention, the step S9 includes the following steps:

-   -   S9.1, calculating the dynamic viscosity η_(0i) of an emulsion         between roll gaps of each rolling stand, wherein         η_(0i)=b·exp(−a·T_(i)), in the formula, a,b are the dynamic         viscosity parameters of lubricating oil under atmospheric         pressure;     -   S9.2, calculating the oil film thickness ξ_(i) between the roll         gaps of each rolling stand, wherein the calculation formula is         as follows:

$\xi_{i} = {{\frac{h_{0i} + h_{1i}}{2h_{0i}} \cdot k_{c} \cdot \frac{3{{\theta\eta}_{0i}\left( {v_{ri} + v_{0i}} \right)}}{\alpha_{i}\left\lbrack {1 - e^{- {\theta({K - \frac{T_{0i}}{h_{0i} \cdot B}})}}} \right\rbrack}} - {k_{rg} \cdot \left( {1 + K_{rs}} \right) \cdot {Ra}_{{ir}0} \cdot e^{{- B_{L}} \cdot L_{i}}}}$ in the formula, k_(rg) represents the coefficient of the strength of entrainment of lubricant by the longitudinal surface roughness of the work roll and the strip steel, and is in the range of 0.09-0.15, and K_(rs) represents the impression rate, that is, the ratio of transferring the surface roughness of the working roll to the strip; and

-   -   S9.3, calculating an emulsion flow rate comprehensive         optimization objective function

$\left\{ \begin{matrix} {{F(X)} = {{\frac{\lambda}{n}{\sum\limits_{i = 1}^{n}\sqrt{\left( {\xi_{i} - \xi_{0i}} \right)^{2}}}} + {\left( {1 - \lambda} \right)\max{❘{\xi_{i} - \xi_{0i}}❘}}}} \\ {\xi_{i}^{-} < \xi_{i} < \xi_{i}^{+}} \end{matrix} \right.$ in the formula, X={w_(i)} is the optimization variable and λ is the distribution coefficient.

In the present application, as long as the next step is not conditional on the result of the previous step, it is not necessary to follow the steps, unless the next step depends on the previous step.

(III) Beneficial Effects

the technical solution of the invention is adopted, and the emulsion flow optimization method for suppressing vibration of the cold continuous rolling mill fully combines the device and process features of the cold continuous rolling mill, and aiming at the problems of vibration defects, starting from the comprehensive optimization setting for the emulsion flow rate of each rolling stand and changing the previous idea of constant emulsion flow control for each rolling stand of the cold continuous rolling mill, the method obtains the optimal set value of the emulsion flow rate for each rolling stand that aims to achieve vibration suppression by optimization; and the method greatly reduces the incidence of rolling mill vibration defects, improves production efficiency and product quality, brings greater economic benefits for enterprises, treats rolling mill vibration defects, and improves the surface quality and rolling process stability of a finished strip of a cold continuous rolling mill.

BRIEF DESCRIPTION OF THE DRAWINGS

In the present invention, the same reference numerals always represent the same features, wherein:

FIG. 1 is a flowchart of an emulsion flow optimization method of the present invention;

FIG. 2 is a flowchart of calculating the vibration determination index reference value;

FIG. 3 is a flowchart of calculating the strip outlet temperature of each rolling stand; and

FIG. 4 is a flowchart of calculating an emulsion flow comprehensive optimization objective function.

DETAILED DESCRIPTION

The technical solution of the present invention will be further described in combination with the drawings and the embodiments.

Rolling mill vibration defects are very easily caused between roll gaps of each rolling stand of a cold continuous rolling mill, whether in an over-lubrication state or in an under-lubrication state, and the setting of the emulsion flow rate directly affects the lubrication state between the roll gaps of each rolling stand. In order to realize the treatment of the rolling mill vibration defects, starting from the emulsion flow rate, this patent ensures that both the overall lubrication state of the cold continuous rolling mill and the lubrication state of individual rolling stands can be optimum through the comprehensive optimal distribution of the emulsion flow rate of the cold continuous rolling mill, so as to achieve the goal of treating the rolling mill vibration defects, improving the surface quality and rolling process stability of a finished strip of the cold continuous rolling mill.

Referring to FIG. 1 , an emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill includes the following steps:

-   -   S1, collecting device feature parameters of the cold continuous         rolling mill, wherein the device feature parameters include: the         radius R_(i) of a working roll of each rolling stand, the         surface linear velocity v_(ri) of a roll of each rolling stand,         the original roughness Ra_(ir0) of a working roll of each         rolling stand, the roughness attenuation coefficient B_(L) of a         working roll, the distance l between rolling stands, and the         rolling kilometer L_(i) after roll change of a working roll of         each rolling stand, wherein i is 1, 2, . . . , n, and represents         for the ordinal number of rolling stands of the cold continuous         rolling mill, and n is the total number of rolling stands;     -   S2, collecting key rolling process parameters of a strip,         wherein the key rolling process parameters include: the inlet         thickness h_(0i) of each rolling stand, the outlet thickness         h_(1i) of each rolling stand, strip width B, the inlet speed         v_(0i) of each rolling stand, the outlet speed v_(1i) of each         rolling stand, the inlet temperature T₁ ^(r), strip deformation         resistance K_(i) of each rolling stand, rolling pressure P_(i)         of each rolling stand, back tension T_(0i) of each rolling         stand, front tension T_(1i) of each rolling stand, emulsion         concentration influence coefficient k_(c), pressure-viscosity         coefficient θ of a lubricant, strip density ρ, specific heat         capacity S of a strip, emulsion concentration C, emulsion         temperature T_(c) and thermal-work equivalent J;     -   S3, defining process parameters involved in the process of         emulsion flow optimization, wherein the process parameters         include that an over-lubrication film thickness critical value         of each rolling stand is ξ_(i) ⁺ and the friction coefficient at         this time is u_(i) ⁺, an under-lubrication film thickness         critical value is ξ_(i) ⁺ and the friction coefficient at this         time is u_(i) ⁻, the rolling reduction amount is         Δh_(i)=h_(0i)−h_(1i), the rolling reduction rate is

${\varepsilon_{i} = \frac{\Delta h_{i}}{h_{0i}}},$ the inlet temperature of each rolling stand is T_(i) ^(r), the distance l between the rolling stands is evenly divided into m sections, and the temperature in the sections is represented by T_(i,j) (wherein, 1≤j≤m), and T_(i) ^(r)=T_(i−1,m), the over-lubrication judgment coefficient is A⁺, and the under-lubrication judgment coefficient is A⁻;

-   -   S4, setting the initial set value of an emulsion flow rate         comprehensive optimization objective function of the cold         continuous rolling mill that aims to achieve vibration         suppression as F₀=1.0×10¹⁰;         the executing order of steps S1 to S4 is not limited, and in         some cases, steps S1 to S4 can be performed simultaneously.     -   S5, calculating the bite angle α_(i) of each rolling stand         according to the rolling theory, wherein the calculation formula         is as follows:

${\alpha_{i} = \sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}},R_{i}^{\prime}$ is the flattening radius of the working roll of the i^(th) rolling stand, and is the calculation process value of rolling pressure;

-   -   S6, calculating the vibration determination index reference         value ξ_(0i) of each rolling stand, wherein the calculation         flowchart is shown in FIG. 2 ;     -   S6.1, calculating the neutral angle γ_(i) of each rolling stand:

${\gamma_{i} = {\frac{1}{2}{\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}\left\lbrack {1 + {\frac{1}{2u_{i}}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}} \right\rbrack}}};$

-   -   S6.2, calculating to obtain

$u_{i}^{+} = {\frac{1}{2\left( {{2A^{+}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = A^{+}},$ the roll gap is just in an over-lubrication state;

-   -   S6.3, calculating an over-lubrication film thickness critical         value ξ_(i) ⁺ of each rolling stand according to the         relationship formula between the friction coefficient and the         oil film thickness, namely u_(i)=a_(i)+b_(i)·e^(B) ^(i) ^(·ξ)         ^(i) (in the formula, a_(i) is the liquid friction influence         coefficient, b_(i) is the dry friction influence coefficient,         and B_(i) is the friction coefficient attenuation index),         wherein

${\xi_{i}^{+} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{+} - a_{i}}{b_{i}}}};$

-   -   S6.4, calculating to obtain

$u_{i}^{-} = {\frac{1}{2\left( {{2A^{-}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = A^{-}},$ the roll gap is just in an under-lubrication state;

-   -   S6.5, calculating an under-lubrication film thickness critical         value ξ_(i) ⁻ of each rolling stand according to the         relationship formula between the friction coefficient and the         oil film thickness, namely u_(i)=a_(i)+b_(i)·e^(B) ^(i) ^(·ξ)         ^(i) , wherein

${\xi_{i}^{-} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{-} - a_{i}}{b_{i}}}};$ and

-   -   S6.6, calculating the vibration determination index reference         value ξ_(0i) of each rolling stand, wherein

${\xi_{0i} = \frac{\xi_{i}^{+} + \xi_{i}^{-}}{2}};$

-   -   S7, setting the emulsion flow rate w_(i) of each rolling stand;     -   S8, calculating the strip outlet temperature T_(i) of each         rolling stand, wherein the calculation flowchart is shown in         FIG. 3 ,     -   S8.1, calculating the outlet temperature T₁ of the first rolling         stand, wherein

${T_{1} = {T_{1}^{r} + {\frac{1 - \left( {\varepsilon_{1}/4} \right)}{1 - \left( {\varepsilon_{1}/2} \right)} \cdot \frac{K_{1}\ln\left( \frac{1}{1 - \varepsilon_{1}} \right)}{\rho{SJ}}}}};$

-   -   S8.2, enabling i=1;     -   S8.3, calculating the temperature T_(i,1) of the first section         of strip behind the outlet of the i^(th) rolling stand, i.e.         T_(i,1)=T_(i);     -   S8.4, enabling j=2;     -   S8.5, showing the relationship between the temperature of the         j^(th) section and the temperature of the j−1^(th) section by         the following equation:

${\tau_{i,j} = {{{- \frac{2k_{0}w_{i}^{0.264}\exp\left( {9.45 - {{0.1}918C}} \right) \times {1.1}63l}{v_{1i}h_{1i}\rho{Sm}}}{T_{i,{j - 1}}^{- 0.213}\left( {T_{i,{j - 1}} - T_{c}} \right)}} + T_{i,{j - 1}}}},$ wherein k₀ is the influence coefficient of the nozzle shape and spraying angle, and 0.80<k₀<1.2;

-   -   S8.6, determining whether the in-equation j<m is established, if         yes, enabling j=j+1, and then turning to step S8.5; otherwise,         turning to step S8.7;     -   S8.7, obtaining the temperature T_(i,m) of the m^(th) section by         iterative calculation;     -   S8.8, calculating the inlet temperature T_(i+1) ^(r) of the         i+1^(th) rolling stand: T₁₊₁ ^(r)=T_(i,m);     -   S8.9, calculating the outlet temperature T_(i+1) of the i+1^(th)         rolling stand, wherein

${T_{i + 1} = {T_{i + 1}^{r} + {\frac{1 - \left( {\varepsilon_{i + 1}/4} \right)}{1 - \left( {\varepsilon_{i + 1}/2} \right)} \cdot \frac{K_{i + 1}\ln\left( \frac{1}{1 - \varepsilon_{i + 1}} \right)}{\rho{SJ}}}}};$

-   -   S8.10, determining whether the in-equation i<n is established,         if yes, enabling i=i+1, and then turning to step S8.3;         otherwise, turning to step S8.11; and     -   S8.11, obtaining the outlet temperature T_(i) of each rolling         stand;     -   S9, calculating an emulsion flow rate comprehensive optimization         objective function F(X), wherein the calculation flowchart is         shown in FIG. 4 ,     -   S9.1, calculating the dynamic viscosity η_(0i) of an emulsion         between roll gaps of each rolling stand, wherein         η_(0i)=b·exp(−a·T_(i)), in the formula, a,b are the dynamic         viscosity parameters of lubricating oil under atmospheric         pressure;     -   S9.2, calculating the oil film thickness ξ_(i) between the roll         gaps of each rolling stand, wherein the calculation formula is         as follows:

$\xi_{i} = {{\frac{h_{0i} + h_{1i}}{2h_{0i}} \cdot k_{c} \cdot \frac{3\theta{\eta_{0i}\left( {v_{ri} + v_{0i}} \right)}}{\alpha_{i}\left\lbrack {1 - e^{- {\theta({K - \frac{T_{0i}}{h_{0i} \cdot B}})}}} \right\rbrack}} - {k_{rg} \cdot \left( {1 + K_{rs}} \right) \cdot {Ra}_{{ir}0} \cdot e^{{- B_{L}} \cdot L_{i}}}}$ in the formula, k_(rg) represents the coefficient of the strength of entrainment of lubricant by the longitudinal surface roughness of the work roll and the strip steel, and is in the range of 0.09-0.15, and K_(rs) represents the impression rate, that is, the ratio of transferring the surface roughness of the working roll to the strip; and

-   -   S9.3, calculating an emulsion flow rate comprehensive         optimization objective function:

$\left\{ \begin{matrix} {{{{F(X)} =}\frac{\lambda}{n}{\sum\limits_{i = 1}^{n}\sqrt{\left( {\xi_{i} - \xi_{0i}} \right)^{2}}}} + {\left( {1 - \lambda} \right)\max{❘{\xi_{i}\  - \xi_{0i}}❘}}} \\ {{\xi_{i}}^{-} < \xi_{i}\  < \xi_{i}^{+}} \end{matrix} \right.$ in the formula, X={w_(i)} is the optimization variable and λ is the distribution coefficient;

-   -   S10, determining whether the in-equation F(X)<F₀ is established,         if yes, enabling w_(i) ^(y)=w_(i), F₀=F(X), and then turning to         step S11; otherwise, turning directly to step S11;     -   S11, determining whether the emulsion flow rate w_(i) exceeds         the a feasible region range, if yes, turning to step S12;         otherwise, turning to step S7, wherein the feasible region of         w_(i) ranges from 0 to the maximum emulsion flow rate value         allowed by the rolling mill.     -   S12, outputting an optimal emulsion flow rate set value w_(i)         ^(y), wherein w_(i) ^(y) is the value of w_(i) when the         calculated value of F(X) in the feasible region is minimum.

Embodiment 1

In order to further explain the application process of the related technology of the present application, the application process of an emulsion flow optimization method for a cold continuous rolling mill that aims to achieve vibration suppression is described by taking a 1730 cold continuous rolling mill in a cold rolling plant as an example.

An emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill includes the following steps:

S1, collecting device feature parameters of the cold continuous rolling mill, wherein the 1730 cold continuous rolling mill in a cold rolling plant has 5 rolling stands in total, and the device feature parameters mainly include: the radius R_(i)={210,212,230,230,228} mm of a working roll of each rolling stand, the surface linear velocity v_(ri)={180,320,500,800,1150} m/min of a roll of each rolling stand, the original roughness Ra_(ir0)={1.0,1.0,0.8,0.8,1.0} um of a working roll of each rolling stand, the roughness attenuation coefficient B_(L)=0.01 of a working roll, the distance l=2700 mm between rolling stands, and the rolling kilometer L_(i)={100,110,230,180,90} km after roll change of a working roll of each rolling stand, wherein i is 1, 2, . . . , n, and represents the ordinal number of rolling stands of the cold continuous rolling mill, and n=5 is the total number of rolling stands, the same below;

-   -   S2, collecting key rolling process parameters of a strip,         wherein the key rolling process parameters mainly include: the         inlet thickness h_(0i)={2.0,1.14,0.63,0.43,0.28} mm of each         rolling stand, the outlet thickness         h_(1i)={1.14,0.63,0.43,0.28,0.18} mm of each rolling stand,         strip width B=966 mm, the inlet speed         v_(0i)={110,190,342,552,848} m/min of each rolling stand, the         outlet speed v_(1i)={190,342,552,848,1214} m/min of each rolling         stand, the inlet temperature T₁ ^(r)=110° C., strip deformation         resistance K_(i)={360,400,480,590,650} MPa of each rolling         stand, rolling pressure P_(i)={12800,11300,10500,9600,8800} kN         of each rolling stand, back tension T_(0i)={70,145,208,202,229}         MPa of each rolling stand, front tension         T_(1i)={145,208,202,229,56} MPa of each rolling stand, emulsion         concentration influence coefficient k_(c)=0.9,         pressure-viscosity coefficient θ=0.034 of a lubricant, strip         density ρ=7800 kg/m³, specific heat capacity S=0.47 kJ/(kg·° C.)         of a strip, emulsion concentration C=4.2%, emulsion temperature         T_(c)=58° C. and thermal-work equivalent J=1;     -   S3, defining process parameters involved in the process of         emulsion flow optimization, wherein the process parameters         mainly include that an over-lubrication film thickness critical         value of each rolling stand is ξ_(i) ⁺ and the friction         coefficient at this time is u_(i) ⁺, an under-lubrication film         thickness critical value is ξ_(i) ⁻ and the friction coefficient         at this time is u_(i) ⁻, the rolling reduction amount is         Δh_(i)=h_(0i)−h_(1i), the rolling reduction rate is

${\varepsilon_{i} = \frac{\Delta h_{i}}{h_{0i}}},$ the inlet temperature of each rolling stand is T_(i) ^(r), and the distance l=2700 mm between the rolling stands is evenly divided into m=30 sections, and the temperature in the sections is represented by T_(i,j) (wherein, 1≤j≤m), and T_(i) ^(r)=T_(i−1,m), the over-lubrication judgment coefficient is A⁺, and the under-lubrication judgment coefficient is A⁻;

-   -   S4, setting the initial set value of an emulsion flow rate         comprehensive optimization objective function of the cold         continuous rolling mill that aims to achieve vibration         suppression as F₀=1.0×10¹⁰;     -   S5, calculating the bite angle α_(i) of each rolling stand         according to the rolling theory, wherein the calculation formula         is

${\alpha_{i} = \sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}},$ from which it can be obtained that α_(i)={0.0556,0.0427,0.0258,0.0223,0.0184};

-   -   S6, calculating the vibration determination index reference         value ξ_(0i) of each rolling stand;     -   S6.1, calculating the neutral angle γ_(i) of each rolling stand,         wherein the calculation formula is

${\gamma_{i} = {\frac{1}{2}{\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}\left\lbrack {1 + {\frac{1}{2u_{i}}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}} \right\rbrack}}};$

-   -   S6.2, calculating to obtain u_(i)         ⁺={0.0248,0.0186,0.0132,0.0136,0.0191} according to the formula

$u_{i}^{+} = {\frac{1}{2\left( {{2A^{+}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = {A^{+} = 1}},$ the roll gap is just in an over-lubrication state;

-   -   S6.3, calculating an over-lubrication film thickness critical         value ξ_(i) ⁺ each rolling stand according to the relationship         formula between the friction coefficient and the oil film         thickness, i.e. u_(i)=a_(i)+b_(i)·e^(B) ^(i) ^(·ξ*is i) (in the         formula, a_(i) is the liquid friction influence coefficient,         a_(i)=0.0126, b_(i) is the dry friction influence coefficient,         b_(i)=0.1416, and B_(i) is the friction coefficient attenuation         index, B_(i)=−2.4297), wherein the calculation formula is

${\xi_{i}^{+} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{+} - a_{i}}{b_{i}}}},$ from which it can be obtained that: ξ_(i) ⁺={1.009,1.301,2.249,2.039,1.268} um;

-   -   S6.4, calculating to obtain u_(i)         ⁻={0.1240,0.0930,0.0660,0.0680,0.0955} according to the formula

$u_{i}^{-} = {\frac{1}{2\left( {{2A^{-}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = {A^{-} = {0.6}}},$ the roll gap is just in an under-lubrication state;

-   -   S6.5, calculating an under-lubrication film thickness critical         value ξ_(i) ⁻ of each rolling stand according to the         relationship formula between the friction coefficient and the         oil film thickness, i.e. u_(i)=a_(i)+b_(i)·e^(B) ^(i)         ^(·ξ*is i), wherein the calculation formula is

${\xi_{i}^{-} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{-} - a_{i}}{b_{i}}}},$ from which it can be obtained that: ξ_(i) ⁻={0.098,0.233,0.401,0.386,0.220} um;

-   -   S6.6, calculating the vibration determination index reference         value ξ_(0i), wherein

${\xi_{0i} = \frac{\xi_{i}^{+} + \xi_{i}^{-}}{2}},$ from which it can be obtained that: ξ_(0i)={0.554,0.767,1.325,1.213,0.744};

-   -   S7. Setting the emulsion flow rate of each rolling stand to be         w_(i)={900,900,900,900,900} L/min;     -   S8, calculating the strip outlet temperature T_(i) of each         rolling stand,     -   S8.1, calculating the outlet temperature T₁ of the first rolling         stand,

$T_{1} = {{T_{1}^{r} + {\frac{1 - \left( {\varepsilon_{1}/4} \right)}{1 - \left( {\varepsilon_{1}/2} \right)} \cdot \frac{K_{1}\ln\left( \frac{1}{1 - \varepsilon_{1}} \right)}{\rho{SJ}}}} = {{110 + {\frac{1 - \left( {0\text{.43}/4} \right)}{1 - \left( {0\text{.43}/2} \right)} \cdot \frac{360{\ln\left( \frac{1}{1 - {{0.4}3}} \right)}}{7.8 \cdot 0.47 \cdot 1}}} = {172.76{^\circ}{C.}}}}$

-   -   S8.2, enabling i=1;     -   S8.3, calculating the temperature T_(1,1) of the first section         of strip behind the outlet of the first rolling stand, i.e.         T_(i,1)=T_(i)=172.76° C.;     -   S8.4, enabling j=2;     -   S8.5, showing the relationship formula between the temperature         of the j^(th) section and the temperature of the j−1^(th)         section by the following equation:

${T_{i,j} = {{{- \frac{2k_{0}w^{0.264}\exp\left( {9.45 - {0.1918C}} \right) \times {1.1}63l}{v_{1i},{h_{1i}\rho{Sm}}}}{T_{i,{j - 1}}^{- 0.213}\left( {T_{i,{j - 1}} - T_{c}} \right)}} + T_{i,{j - 1}}}},$ wherein k₀=1.0;

-   -   S8.6, determining whether the in-equation j<m is established: if         yes, enabling j=j+1. and then turning to step S8.5; otherwise,         turning to step S8.7;     -   S8.7, obtaining the temperature T_(1,30)=103.32° C. of the         m=30^(th) section by iterative calculation finally;     -   S8.8, calculating the inlet temperature T₂ ^(r) of the second         rolling stand: T₂ ^(r)=T_(1,m)=103.32° C.;     -   S8.9, calculating the outlet temperature T₂ of the second         rolling stand:

${T_{2} = {{T_{2}^{r} + {\frac{1 - \left( {\varepsilon_{2}/4} \right)}{1 - \left( {\varepsilon_{2}/2} \right)} \cdot \frac{K_{2}\ln\left( \frac{1}{1 - \varepsilon_{2}} \right)}{\rho SJ}}} = {{{10{3.3}2} + {\frac{1 - \left( {0\text{.45}/4} \right)}{1 - \left( {0\text{.45}/2} \right)} \cdot \frac{400\ln\left( \frac{1}{1 - {{0.4}5}} \right)}{7800 \cdot 0.47 \cdot 1}}} = {178.02{^\circ}{C.}}}}};$

-   -   S8.10, determining whether the in-equation i<n is established:         if yes, enabling i=i+1, and then turning to step S8.3;         otherwise, turning to step S8.11;     -   S8.11, obtaining the outlet temperature         T_(i)={172.76,178.02,186.59,194.35,206.33}° C. of each rolling         stand;     -   S9, calculating an emulsion flow rate comprehensive optimization         objective function F(X);     -   S9.1, calculating the dynamic viscosity η_(0i) of an emulsion         between roll gaps of each rolling stand, wherein         η_(0i)=b·exp(−a·T_(i)), in the formula, a,b are the dynamic         viscosity parameters of lubricating oil under atmospheric         pressure, and it can be obtained from a=0.05, b=2.5 that         η_(0i)={5.39,5.46,5.59,5.69,5.84};     -   S9.2, calculating the oil film thickness ξ_(i) between the roll         gaps of each rolling stand according to the following formula:

$\xi_{i} = {{\frac{h_{0i} + h_{1i}}{2h_{0i}} \cdot k_{c} \cdot \frac{3\theta{\eta_{0i}\left( {v_{ri} + v_{0i}} \right)}}{\alpha_{i}\left\lbrack {1 - e^{- {\theta({K - \frac{T_{0i}}{h_{0i} \cdot B}})}}} \right\rbrack}} - {k_{rg} \cdot \left( {1 + K_{rs}} \right) \cdot {Ra}_{{ir}0} \cdot e^{{- B_{Li}} \cdot L_{i}}}}$ wherein in the formula, k_(rg) represents the coefficient of the strength of entrainment of lubricant by the longitudinal surface roughness of the work roll and the strip steel, k_(rg)=1.183, and K_(rs) represents the impression rate, that is, the ratio of transferring the surface roughness of the working roll to the strip, K_(rs)=0.576, from which it can be obtained that: ξ_(i)={0.784,0.963,2.101,2.043,1.326} um;

-   -   S9.3, calculating an emulsion flow rate comprehensive         optimization objective function:

$\left\{ \begin{matrix} {{F(X)} = {{\frac{\lambda}{n}{\sum\limits_{i = 1}^{n}\sqrt{\left( {\xi - \xi_{0i}} \right)^{2}}}} + {\left( {1 - \lambda} \right)\max{❘{\xi_{i}\  - \xi_{0i}}❘}}}} \\ {\xi_{i}^{-} < \xi_{i}\  < \xi_{i}^{+}} \end{matrix} \right.$ in the formula, X={w_(i)} is the optimization variable, λ=0.5 is the distribution coefficient, and thus F(X)=0.94;

-   -   S10, enabling w_(i) ^(y)=w_(i)={900,900,900,900,900} L/min if         F(X)=0.94<F₀=1×10¹⁰ is established, F₀=F(X)=0.94, turning to         step S11, wherein in the subsequent x calculation processes, the         corresponding F(X) is obtained with the change of w_(i), and the         x^(th) F₀ is the x−1^(th) F(X). If the x^(th) F(X) is smaller         than the x−1^(th) F(X), it is judged that F(X)<F₀ is established         and turn to step S11;     -   S11, determining whether the emulsion flow rate w_(i) exceeds         the feasible region range. If yes, turning to step S12;         otherwise, turning to step S7; and     -   S12, outputting an optimal emulsion flow rate set value w_(i)         ^(y)={1022,1050,1255,1698,1102} L/min.

Embodiment 2

In order to further explain the application process of the related technology of the present application, the application process of an emulsion flow optimization method for a cold continuous rolling mill that aims to achieve vibration suppression is described by taking a 1420 cold continuous rolling mill in a cold rolling plant as an example.

An emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill includes the following steps:

-   -   S1, collecting device feature parameters of the cold continuous         rolling mill, wherein the 1420 cold continuous rolling mill in a         cold rolling plant has 5 rolling stands in total, and the device         feature parameters mainly include: the radius         R_(i)={211,213,233,233,229} mm of a working roll of each rolling         stand, the surface linear velocity v_(ri)={182,322,504,805,1153}         m/min of a roll of each rolling stand, the original roughness         Ra_(ir0)={1.0,1.0,0.9,0.9,1.0} um of a working roll of each         rolling stand, the roughness attenuation coefficient B_(L)=0.015         of a working roll, the distance l=2750 mm between rolling         stands, and the rolling kilometer L_(i)={120,130,230,190,200} km         after roll change of a working roll of each rolling stand,         wherein i is 1, 2, . . . , n, and represents the ordinal number         of rolling stands of the cold continuous rolling mill, and n=5         is the total number of rolling stands, the same below;     -   S2, collecting key rolling process parameters of a strip,         wherein the key rolling process parameters mainly include: the         inlet thickness h_(0i)={2.1,1.15,0.65,0.45,0.3} mm of each         rolling stand, the outlet thickness         h_(1i)={1.15,0.65,0.45,0.3,0.15} mm of each rolling stand, strip         width B=955 mm, the inlet speed v_(0i)={115,193,346,555,852}         m/min of each rolling stand, the outlet speed         v_(1i)={191,344,556,849,1217} m/min of each rolling stand, the         inlet temperature T₁ ^(r)=115° C. strip deformation resistance         K_(i)={370,410,490,590,660} MPa of each rolling stand, rolling         pressure P_(i)={12820,11330,10510,9630,8820} kN of each rolling         stand, back tension T_(0i)={73,148,210,205,232}MPa of each         rolling stand, front tension T_(1i)={147,212,206,231,60} MPa of         each rolling stand, emulsion concentration influence coefficient         k_(c)=0.9, pressure-viscosity coefficient θ=0.036 of a         lubricant, strip density ρ=7800 kg/m³, specific heat capacity         S=0.49 kJ/(kg·° C.) of a strip, emulsion concentration C=4.5%,         emulsion temperature T_(c)=59° C. and thermal-work equivalent         J=1;     -   S3, defining process parameters involved in the process of         emulsion flow optimization, wherein the process parameters         mainly include that an over-lubrication film thickness critical         value of each rolling stand is ξ_(i) ⁺ and the friction         coefficient at this time is u_(i) ⁺, an under-lubrication film         thickness critical value is ξ_(i) ⁻ and the friction coefficient         at this time is u_(i) ⁻, the rolling reduction amount is         Δh_(i)=h_(0i)−h_(1i), the rolling reduction rate is

${\varepsilon_{i} = \frac{\Delta h_{i}}{h_{0i}}},$ the inlet temperature of each rolling stand is T_(i) ^(r), the distance l=2750 mm between the rolling stands is evenly divided into m=30 sections, and the temperature in the sections is represented by T_(i,j) (wherein, 1≤j≤m), and T_(i) ^(r)=T_(i−1,m), the over-lubrication judgment coefficient is A⁺, and the under-lubrication judgment coefficient is A⁻;

-   -   S4, setting the initial set value of an emulsion flow rate         comprehensive optimization objective function of a cold         continuous rolling mill that aims to achieve vibration         suppression as F₀=1.0×10¹⁰;     -   S5, calculating the bite angle α_(i) of each rolling stand         according to the rolling theory, wherein the calculation formula         is

${\alpha_{i} = \sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}},$ from which it can be obtained that α_(i)={0.0566,0.0431,0.0261,0.0227,0.0188};

-   -   S6, calculating the vibration determination index reference         value ξ_(0i) of each rolling stand;     -   S6.1, calculating the neutral angle γ_(i) of each rolling stand,         wherein the calculation formula is

${\gamma_{i} = {\frac{1}{2}{\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}\left\lbrack {1 + {\frac{1}{2u_{i}}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}} \right\rbrack}}};$

-   -   S6.2, calculating to obtain u_(i)         ⁺={0.0251,0.0187,0.0135,0.0138,0.0193} according to the formula

$u_{i}^{+} = {\frac{1}{2\left( {{2A^{+}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = {A^{+} = 1}},$ the roll gap is just in an over-lubrication state;

-   -   S6.3, calculating an over-lubrication film thickness critical         value ξ_(i) ⁺ of each rolling stand according to the         relationship formula between the friction coefficient and the         oil film thickness, i.e. u_(i)=a_(i)+b_(i)·e^(B) ^(i) ^(·ξ*is i)         (in the formula, a_(i) is the liquid friction influence         coefficient, a_(i)=0.0128, b_(i) is the dry friction influence         coefficient, b_(i)=0.1426, and B_(i) is the friction coefficient         attenuation index, B_(i)—2.4307), wherein the calculation         formula is

${{\xi_{i}}^{+} = {\frac{1}{B_{i}}\ln\frac{{u_{i}}^{+} - a_{i}}{b_{i}}}},$ from which it can be obtained that: ξ_(i) ⁺={1.011,1.321,2.253,2.041,1.272} um;

-   -   S6.4, calculating to obtain u_(i)         ⁻={0.1243,0.0936,0.0664,0.0685,0.0955} according to the formula

$u_{i}^{-} = {\frac{1}{2\left( {{2A^{-}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = {A^{-} = {0.6}}},$ the roll gap is just in an under-lubrication state;

-   -   S6.5, calculating an under-lubrication film thickness critical         value ξ_(i) ⁻ of each rolling stand according to the         relationship formula between the friction coefficient and the         oil film thickness, i.e. u_(i)=a_(i)+b_(i)·e^(B) ^(i)         ^(·ξ*is i), wherein the calculation formula is

${\xi_{i}^{-} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{-} - a_{i}}{b_{i}}}},$ from which it can be obtained that: ξ_(i) ⁻={0.101,0.236,0.411,0.389,0.223} um;

-   -   S6.6, calculating the vibration determination index reference         value ξ_(0i), wherein

${\xi_{0i} = \frac{\xi_{i}^{+} + \xi_{i}^{-}}{2}},$ from which it can be obtained that: ξ_(0i)={0.557,0.769,1.327,1.215,0.746};

-   -   S7, setting the emulsion flow rate of each rolling stand to be         w_(i)={900,900,900,900,900} L/min;     -   S8, calculating the strip outlet temperature T_(i) of each         rolling stand,     -   S8.1, calculating the outlet temperature T₁ of the first rolling         stand,

$T_{1} = {{T_{1}^{r} + {\frac{1 - \left( {\varepsilon_{1}/4} \right)}{1 - \left( {\varepsilon_{1}/2} \right)} \cdot \frac{K_{1}\ln\left( \frac{1}{1 - \varepsilon_{1}} \right)}{\rho{SJ}}}} = {{110 + {\frac{1 - \left( {0.43/4} \right)}{1 - \left( {0.43/2} \right)} \cdot \frac{360{\ln\left( \frac{1}{1 - 0.43} \right)}}{7.8 \cdot 0.47 \cdot 1}}} = {175.81{^\circ}{C.}}}}$

-   -   S8.2, enabling i=1;     -   S8.3, calculating the temperature T_(1,1) of the first section         of strip behind the outlet of the first rolling stand, i.e.         T_(i,1)=T_(i)=175.81° C.;     -   S8.4, enabling j=2;     -   S8.5, showing the relationship between the temperature of the         j^(th) section and the temperature of the j−1^(th) section by         the following equation:

${T_{i,j} = {{{- \frac{2k_{0}w_{i}^{0.264}\exp\left( {9.45 - {0.1918C}} \right) \times {1.1}63l}{v_{1i}h_{1i}\rho Sm}}{T_{i,{j - 1}}^{- 0.213}\left( {T_{i,{j - 1}} - T_{c}} \right)}} + T_{i,{j - 1}}}},{{{{wherein}k_{0}} = 1.};}$

-   -   S8.6, determining whether the in-equation j<m is established: if         yes, enabling j=j+1. and then turning to step S8.5; otherwise,         turning to step S8.7;     -   S8.7, obtaining the temperature T_(1,30)=105.41° C. of the         m=30^(th) section by iterative calculation finally;     -   S8.8, calculating the inlet temperature T₂ ^(r) of the second         rolling stand: T₂ ^(r)=T_(1,m)=105.41° C.;     -   S8.9, calculating the outlet temperature T₂ of the second         rolling stand

$T_{2} = {{T_{2}^{r} + {\frac{1 - \left( {\varepsilon_{2}/4} \right)}{1 - \left( {\varepsilon_{2}/2} \right)} \cdot \frac{K_{2}\ln\left( \frac{1}{1 - \varepsilon_{2}} \right)}{\rho{SJ}}}} = {{{10{3.3}2} + {\frac{1 - \left( {0.45/4} \right)}{1 - \left( {0.45/2} \right)} \cdot \frac{400\ln\left( \frac{1}{1 - {{0.4}5}} \right)}{7800 \cdot 0.47 \cdot 1}}} = {182.52{^\circ}{C.}}}}$

-   -   S8.10, determining whether the in-equation i<n is established:         if yes, enabling i=i+1, and then turning to step S8.3;         otherwise, turning to step S8.11;     -   S8.11, obtaining the outlet temperature         T_(i)={175.86,179.36,189.77,196.65,207.54}° C. of each rolling         stand;     -   S9, calculating an emulsion flow rate comprehensive optimization         objective function F(X);     -   S9.1, calculating the dynamic viscosity η_(0i) of an emulsion         between roll gaps of each rolling stand, wherein η_(0i)=b·exp         (−a·T_(i)), in the formula, a,b are the dynamic viscosity         parameters of lubricating oil under atmospheric pressure, and it         can be obtained from a=0.15, b=3.0 that         η_(0i)={5.45,5.78,5.65,5.75,5.89};     -   S9.2, calculating the oil film thickness ξ_(i) between the roll         gaps of each rolling stand according to the following formula:

$\xi_{i} = {{\frac{h_{0i} + h_{1i}}{2h_{0i}} \cdot k_{c} \cdot \frac{3\theta{\eta_{0i}\left( {v_{ri} + v_{0i}} \right)}}{\alpha_{i}\left\lbrack {1 - e^{- {\theta({K - \frac{T_{0i}}{h_{0i} \cdot B}})}}} \right\rbrack}} - {k_{rg} \cdot \left( {1 + K_{rs}} \right) \cdot {Ra}_{{ir}0} \cdot e^{{- B_{Li}} \cdot L_{i}}}}$ wherein in the formula, k_(rg) represents the coefficient of the strength of entrainment of lubricant by the longitudinal surface roughness of the work roll and the strip steel, k_(rg)=1.196, and K_(rs) represents the impression rate, that is, the ratio of transferring the surface roughness of the working roll to the strip, K_(rs)=0.584, from which it can be obtained that: ξ_(i)={0.795,0.967,2.132,2.056,1.337} um;

-   -   S9.3, calculating an emulsion flow rate comprehensive         optimization objective function:

$\left\{ \begin{matrix} {{{{F(X)} =}\frac{\lambda}{n}{\sum\limits_{i = 1}^{n}\sqrt{\left( {\xi_{i} - \xi_{0i}} \right)^{2}}}} + {\left( {1 - \lambda} \right)\max{❘{\xi_{i}\  - \xi_{0i}}❘}}} \\ {\xi_{i}^{-} < \xi_{i}\  < \xi_{i}^{+}} \end{matrix} \right.$ in the formula, X={w_(i)} is the optimization variable, λ=0.5 is the distribution coefficient, and thus F(X)=0.98;

-   -   S10, enabling w_(i) ^(y)=w_(i)={900,900,900,900,900} L/min if         F(X)=0.98<F₀=1×10¹⁰ is established, F₀=F(X)=0.98, turning to         step S11, wherein in the subsequent x calculation processes, the         corresponding F(X) is obtained with the change of w_(i), and the         x^(th) F₀ is the x−1^(th) F(X). If the x^(th) F(X) is smaller         than the x−1^(th) F(X), it is judged that F(X)<F₀ is established         and turn to step S11;     -   S11, determining whether the emulsion flow rate w_(i) exceeds         the feasible region range. If yes, turning to step S12;         otherwise, turning to step S7; and     -   S12, outputting an optimal emulsion flow rate set value w_(i)         ^(y)={1029,1055,1261,1703,1109} L/min.

Embodiment 3

In order to further explain the application process of the related technology of the present application, the application process of an emulsion flow optimization method for a cold continuous rolling mill that aims to achieve vibration suppression is described by taking a 1220 cold continuous rolling mill in a cold rolling plant as an example.

An emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill includes the following steps:

-   -   S1, collecting device feature parameters of the cold continuous         rolling mill, wherein the 1220 cold continuous rolling mill in a         cold rolling plant has 5 rolling stands in total, and the device         feature parameters mainly include: the radius         R_(i)={208,210,227,226,225} mm of a working roll of each rolling         stand, the surface linear velocity v_(ri)={176,317,495,789,1146}         m/min of a roll of each rolling stand, the original roughness         Ra_(ir0)={0.9,0.9,0.7,0.7,0.8} um of a working roll of each         rolling stand, the roughness attenuation coefficient B_(L)=0.01         of a working roll, the distance l=2700 mm between rolling         stands, and the rolling kilometer L_(i)={152,102,215,165,70} km         after roll change of a working roll of each rolling stand,         wherein i is 1, 2, . . . , n, and represents the ordinal number         of rolling stands of the cold continuous rolling mill, and n=5         is the total number of rolling stands, the same below;     -   S2, collecting key rolling process parameters of a strip,         wherein the key rolling process parameters mainly include: the         inlet thickness h_(0i)={1.8,1.05,0.57,0.39,0.25} mm of each         rolling stand, the outlet thickness         h_(1i)={1.05,0.57,0.36,0.22,0.13} mm of each rolling stand,         strip width B=876 mm, the inlet speed         v_(0i)={104,185,337,546,844} m/min of each rolling stand, the         outlet speed v_(1i)={188,337,548,845,1201}m/min of each rolling         stand, the inlet temperature T₁ ^(r)=110° C. strip deformation         resistance K_(i)={355,395,476,580,640} MPa of each rolling         stand, rolling pressure P_(i)={12900,11200,10400,9600,8900} kN         of each rolling stand, back tension T_(0i)={74,141,203,201,219}         MPa of each rolling stand, front tension         T_(1i)={140,203,199,224,50} MPa of each rolling stand, emulsion         concentration influence coefficient k_(c)=0.8,         pressure-viscosity coefficient θ=0.035 of a lubricant, strip         density ρ=7800 kg/m³, specific heat capacity S=0.45 kJ/(kg·° C.)         of a strip, emulsion concentration C=3.7%, emulsion temperature         T_(c)=55° C. and thermal-work equivalent J=1;     -   S3, defining process parameters involved in the process of         emulsion flow optimization, wherein the process parameters         mainly include that an over-lubrication film thickness critical         value of each rolling stand is ξ_(i) ⁺ and the friction         coefficient at this time is u_(i) ⁺, an under-lubrication film         thickness critical value is ξ_(i) ⁻ and the friction coefficient         at this time is u_(i) ⁻, the rolling reduction amount is         Δh_(i)=h_(0i)−h_(1i), the rolling reduction rate is

${\varepsilon_{i} = \frac{\Delta h_{i}}{h_{0i}}},$ the inlet temperature of each rolling stand is T_(i) ^(r), the distance l=2700 mm between the rolling stands is evenly divided into m=30 sections, and the temperature in the sections is represented by T_(i,j) (wherein, 1≤j≤m), and T_(i) ^(r)=T_(i+1,m), the over-lubrication judgment coefficient is A⁺, and the under-lubrication judgment coefficient is A⁻;

-   -   S4, setting the initial set value of an emulsion flow rate         comprehensive optimization objective function of a cold         continuous rolling mill that aims to achieve vibration         suppression as F₀=1.0×10¹⁰;     -   S5, calculating the bite angle α_(i) of each rolling stand         according to the rolling theory, wherein the calculation formula         is

${\alpha_{i} = \sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}},$ from which it can be obtained that α_(i)={0.0546,0.0406,0.0247,0.0220,0.0179};

-   -   S6, calculating the vibration determination index reference         value ξ_(0i) of each rolling stand;     -   S6.1, calculating the neutral angle γ_(i) of each rolling stand,         wherein the calculation formula is

${\gamma_{i} = {\frac{1}{2}{\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}\left\lbrack {1 + {\frac{1}{2u_{i}}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}} \right\rbrack}}};$

-   -   S6.2, calculating to obtain u_(i)         ⁺={0.0242,0.0179,0.0127,0.0130,0.0185} according to the formula

$u_{i}^{+} = {\frac{1}{2\left( {{2A^{+}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = {A^{+} = 1}},$ the roll gap is just in an over-lubrication state;

-   -   S6.3, calculating an over-lubrication film thickness critical         value ξ_(i) ⁺ of each rolling stand according to the         relationship formula between the friction coefficient and the         oil film thickness, i.e. u_(i)=a_(i)=b_(i)·e^(B) ^(i) ^(·ξ) ^(i)         (in the formula, a_(i) is the liquid friction influence         coefficient, a_(i)=0.0125, b_(i) is the dry friction influence         coefficient, b_(i)=0.1414, and B_(i) is the friction coefficient         attenuation index, B_(i)=−2.4280), wherein the calculation         formula is

${\xi_{i}^{+} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{+} - a_{i}}{b_{i}}}},$ from which it can be obtained that: ξ_(i) ⁺={1.001,1.289,2.232,2.037,1.268} um;

-   -   S6.4, calculating to obtain u_(i)         ⁻={0.1241,0.0922,0.0610,0.0630,0.0935} according to the formula

$u_{i}^{-} = {\frac{1}{2\left( {{2A^{-}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from steps S5 and S6.1 assuming that when

${\frac{\gamma_{i}}{\alpha_{i}} = {A^{-} = {0.6}}},$ the roll gap is just in an under-lubrication state;

-   -   S6.5, calculating an under-lubrication film thickness critical         value ξ_(i) ⁻ of each rolling stand according to the         relationship between the friction coefficient and the oil film         thickness, i.e. u_(i)=a_(i)=b_(i)·e^(B) ^(i) ^(·ξ) ^(i) ,         wherein the calculation formula is

${\xi_{i}^{-} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{-} - a_{i}}{b_{i}}}},$ from which it can be obtained that: ξ_(i) ⁻={0.097,0.223,0.398,0.385,0.210} um;

-   -   S6.6, calculating the vibration determination index reference         value ξ_(0i), wherein

${\xi_{0i} = \frac{\xi_{i}^{+} + \xi_{i}^{-}}{2}},$ from which it can be obtained that: ξ_(0i)={0.548,0.762,1.321,1.207,0.736};

-   -   S7, setting the emulsion flow rate of each rolling stand to be         w_(i)={900,900,900,900,900} L/min;     -   S8, calculating the strip outlet temperature T_(i) of each         rolling stand,     -   S8.1, calculating the outlet temperature T₁ of the first rolling         stand,

$T_{1} = {{T_{1}^{r} + {\frac{1 - \left( {\varepsilon_{1}/4} \right)}{1 - \left( {\varepsilon_{1}/2} \right)} \cdot \frac{K_{1}\ln\left( \frac{1}{1 - \varepsilon_{1}} \right)}{\rho{SJ}}}} = {{110 + {\frac{1 - \left( {0.43/4} \right)}{1 - \left( {0.43/2} \right)} \cdot \frac{360{\ln\left( \frac{1}{1 - 0.43} \right)}}{7.8 \cdot 0.47 \cdot 1}}} = {169.96{^\circ}{C.}}}}$

-   -   S8.2, enabling i=1;     -   S8.3, calculating the temperature T_(1,1) of the first section         of strip behind the outlet of the first rolling stand, i.e.         T_(i,1)=T_(i)=169.96° C.;     -   S8.4, enabling j=2;     -   S8.5, showing the relationship between the temperature of the         j^(th) section and the temperature of the j−1^(th) section by         the following equation:

${T_{i,j} = {{{- \frac{2k_{0}w_{i}^{0.264}{\exp\left( {9.45 - {0.1918C}} \right)} \times {1.1}63l}{v_{1i}h_{1i}\rho{Sm}}}{T_{i,{j - 1}}^{- 0.213}\left( {T_{i,{j - 1}} - T_{c}} \right)}} + T_{i,{j - 1}}}},$ wherein k₀=1.0;

-   -   S8.6, determining whether the in-equation j<m is established: if         yes, enabling j=j+1. and then turning to step S8.5; otherwise,         turning to step S8.7;     -   S8.7, obtaining the temperature T_(1,30)=101.25° C. of the         m=30^(th) section by iterative calculation finally;     -   S8.8, calculating the inlet temperature T₂ ^(r) of the second         rolling stand: T₂ ^(r)=T_(1,m)=101.25° C.;     -   S8.9, calculating the outlet temperature T₂ of the second         rolling stand:

$T_{2} = {{T_{2}^{r} + {\frac{1 - \left( {\varepsilon_{2}/4} \right)}{1 - \left( {\varepsilon_{2}/2} \right)} \cdot \frac{K_{2}\ln\left( \frac{1}{1 - \varepsilon_{2}} \right)}{\rho SJ}}} = {{{10{3.3}2} + {\frac{1 - \left( {0.45/4} \right)}{1 - \left( {0.45/2} \right)} \cdot \frac{400\ln\left( \frac{1}{1 - {{0.4}5}} \right)}{7800 \cdot 0.47 \cdot 1}}} = {175.86{^\circ}{C.}}}}$

-   -   S8.10, determining whether the in-equation i<n is established:         if yes, enabling i=i+1, and then turning to step S8.3;         otherwise, turning to step S8.11;     -   S8.11, obtaining the outlet temperature         T_(i)={177.96,172.78,184.59,191.77,203.33}° C. of each rolling         stand;     -   S9, calculating an emulsion flow rate comprehensive optimization         objective function F(X);     -   S9.1, calculating the dynamic viscosity η_(0i) of an emulsion         between roll gaps of each rolling stand, wherein         η_(0i)=b·exp(−a·T_(i)), in the formula, a,b are the dynamic         viscosity parameter of lubricating oil under atmospheric         pressure, and it can be obtained from a=0.15, b=2.0 that         η_(0i)={5.45,5.02,5.98,5.45,5.76};     -   S9.2, calculating the oil film thickness ξ_(i) between the roll         gaps of each rolling stand according to the following formula:

$\xi_{i} = {{\frac{h_{0i} + h_{1i}}{2h_{0i}} \cdot k_{c} \cdot \frac{3\theta{\eta_{0i}\left( {v_{ri} + v_{0i}} \right)}}{\alpha_{i}\left\lbrack {1 - e^{- {\theta({K - \frac{T_{0i}}{h_{0i} \cdot B}})}}} \right\rbrack}} - {k_{rg} \cdot \left( {1 + K_{rs}} \right) \cdot {Ra}_{{ir}0} \cdot e^{{- B_{Li}} \cdot L_{i}}}}$ wherein in the formula, k_(rg) represents the coefficient of the strength of entrainment of lubricant by the longitudinal surface roughness of the work roll and the strip steel, k_(rg)=1.165, and K_(rs) represents the impression rate, that is, the ratio of transferring the surface roughness of the working roll to the strip, K_(rs)=0.566, from which it can be obtained that: ξ_(i)={0.774,0.926,2.088,2.032,1.318} um ; S9.3, calculating an emulsion flow rate comprehensive optimization objective function:

$\left\{ \begin{matrix} {{F(X)} = {{\frac{\lambda}{n}{\sum\limits_{i = 1}^{n}\sqrt{\left( {\xi_{i} - \xi_{0i}} \right)^{2}}}} + {\left( {1 - \lambda} \right)\max{❘{\xi_{i}\  - \xi_{0i}}❘}}}} \\ {\xi_{i}^{-} < \xi_{i}\  < \xi_{i}^{+}} \end{matrix} \right.$ In the formula, X={w_(i)} is the optimization variable, λ=0.5 is the distribution coefficient, and thus F(X)=0.91;

-   -   S10, enabling w_(i) ^(y)=w_(i)={900,900,900,900,900} L/min if         F(X)=0.91<F₀=1×10¹⁰ is established, F₀=F(X)=0.91, turning to         step S11, wherein in the subsequent x calculation processes, the         corresponding F(X) is obtained with the change of w_(i), and the         x^(th) F₀ is the x−1^(th) F(X). If the x^(th) F(X) is smaller         than the x−1^(th) F(X), it is judged that F(X)<F₀ is established         and turn to step S11;     -   S11, determining whether the emulsion flow rate w_(i) exceeds         the feasible region range. If yes, turning to step S12;         otherwise, turning to step S7; and     -   S12, outputting an optimal emulsion flow rate set value w_(i)         ^(y)={1016,1040,1266,1681,1111}L /min .

The invention is applied to the five-machine-frame cold continuous rolling mills 1730, 1420 and 1220 in the cold rolling plant. According to the production experience of the cold rolling plant, the solution of the invention is feasible, and the effect is very obvious. The invention can be further applied to other cold continuous rolling mills, and the popularization prospect is relatively broad.

To sum up, the technical solution of the invention is adopted, and the emulsion flow optimization method for suppressing vibration of the cold continuous rolling mill fully combines the device and process features of the cold continuous rolling mill, and aiming at the vibration defect problem, starting from the comprehensive optimization setting of the emulsion flow rate of each rolling stand, the method changes the previous idea of constant emulsion flow control for each rolling stand of the cold continuous rolling mill, and obtains the optimal set value of the emulsion flow rate for each rolling stand that aims to achieve vibration suppression by optimization; and the method greatly reduces the incidence of rolling mill vibration defects, improves production efficiency and product quality, and brings greater economic benefits for enterprises; and achieves the treatment for rolling mill vibration defects, and improves the surface quality and rolling process stability of a finished strip of a cold continuous rolling mill. 

The invention claimed is:
 1. An emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill, comprising the following steps: (S1) collecting device feature parameters of the cold continuous rolling mill, wherein the device feature parameters comprise: a radius R_(i) of a working roll of each of a plurality of rolling stands, a surface linear velocity v_(ri) of a roll of each rolling stand, a original roughness Ra_(ir0) of a working roll of each rolling stand, a roughness attenuation coefficient B_(L) of a working roll, a distance l between rolling stands, and a rolling kilometer L_(i) after roll change of a working roll of each rolling stand, wherein i is 1, 2, . . . , n, and represents an ordinal number of the rolling stands of the cold continuous rolling mill, and n is the total number of rolling stands; (S2) collecting key rolling process parameters of a strip, wherein the key rolling process parameters comprise: an inlet thickness h_(0i) of each rolling stand, an outlet thickness h_(1i) of each rolling stand, a strip width B, an inlet speed v_(0i) of each rolling stand, an outlet speed v_(1i) of each rolling stand, an inlet temperature T₁ ^(r), a strip deformation resistance K_(i) of each rolling stand, a rolling pressure P_(i) of each rolling stand, a back tension T_(0i) of each rolling stand, a front tension T_(1i) of each rolling stand, an emulsion concentration influence coefficient k_(c), a pressure-viscosity coefficient θ of a lubricant, a strip density ρ, a specific heat capacity S of a strip, an emulsion concentration C, an emulsion temperature T_(c) and a thermal-work equivalent J; (S3) defining process parameters involved in an emulsion flow optimization process, wherein the process parameters comprise an over-lubrication film thickness critical value ξ_(i) ⁺ of each rolling stand, a first friction coefficient u_(i) ⁺ at this time, an under-lubrication film thickness critical value ξ_(i) ⁻ and a second friction coefficient u_(i) ⁻ at this time, a rolling reduction amount Δh_(i) (wherein Δh_(i)=h_(0i)−h_(1i)), a rolling reduction rate ε_(i) (wherein $\varepsilon_{i} = \frac{\Delta h_{i}}{h_{0i}}$ ), an inlet temperature T_(i) ^(r) of each rolling stand, an over-lubrication judgment coefficient A⁺, and an under-lubrication judgment coefficient A⁻, and evenly dividing the distance l between the rolling stands into m sections, wherein a temperature in the sections is represented by T_(i,j) (wherein 1≤j≤m, and T_(i) ^(r)=T_(i−1,m)); (S4) setting an initial set value of an emulsion flow rate comprehensive optimization objective function of the cold continuous rolling mill for achieving a vibration suppression as F₀=1.0×10¹⁰; wherein an executing order of steps S1-S4 is not limited; (S5) calculating a bite angle α_(i) of each rolling stand according to a rolling theory, wherein a calculation formula is as follows: $\alpha_{i} = {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}},}R_{i}^{\prime}}$ is a flattening radius of a working roll of an i^(th) rolling stand, and is a calculation process value of rolling pressure; (S6) calculating a vibration determination index reference value ξ_(0i) of each rolling stand; (S7) setting an emulsion flow rate w_(i) of each rolling stand; (S8) calculating a strip outlet temperature T_(i) of each rolling stand; (S9) calculating an emulsion flow rate comprehensive optimization objective function F(X); $\left\{ {\begin{matrix} {{F(X)} = {{\frac{\lambda}{n}{\sum\limits_{i = 1}^{n}\sqrt{\left( {\xi_{i} - \xi_{0i}} \right)^{2}}}} + {\left( {1 - \lambda} \right)\max{❘{\xi_{i} - \xi_{0i}}❘}}}} \\ {\xi_{i}^{-} < \xi_{i} < \xi_{i}^{+}} \end{matrix};} \right.$ (S10) determining whether an in-equation F(X)<F₀ is established, if yes, enabling w_(i) ^(y)=w_(i), F₀=F(X), and turning to step S11; otherwise, directly turning to step S11; (S11) determining whether an emulsion flow rate w_(i) exceeds a feasible region range, if yes, turning to step S12, otherwise, turning to step S7, wherein a feasible region of w_(i) ranges from 0 to a maximum emulsion flow rate value allowed by the rolling mill; and (S12) outputting an optimum emulsion flow rate set value w_(i) ^(y), wherein w_(i) ^(y) is the value of w_(i) when a calculated value of F(X) in the feasible region is minimum.
 2. The emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill according to claim 1, wherein the step S6 comprises the following steps: (S6.1) calculating a neutral angle γ_(i) of each rolling stand: ${\gamma_{i} = {\frac{1}{2}{\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}}\left\lbrack {1 + {\frac{1}{2u_{i}}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}} \right\rbrack}}};$ (S6.2) calculating to obtain $u_{i}^{+} = {\frac{1}{2\left( {{2A^{+}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from the step S5 and the step S6.1 assuming that when ${\frac{\gamma_{i}}{\alpha_{i}} = A^{+}},$ a roll gap is just in an over-lubrication state; (S6.3) calculating an over-lubrication film thickness critical value ξ_(i) ⁺ of each rolling stand according to a relation formula between the first friction coefficient u_(i) ⁺ and an oil film thickness wherein u_(i) ⁺=a_(i)+b_(i)·e^(B) ^(i) ^(·ξ) ^(i) ⁺ in the formula, a_(i) is a liquid friction influence coefficient, b_(i) is a dry friction influence coefficient, and B_(i) is a friction coefficient attenuation index, and wherein ${\xi_{i}^{+} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{+} - a_{i}}{b_{i}}}};$ (S6.4) calculating to obtain $u_{i}^{-} = {\frac{1}{2\left( {{2A^{-}} - 1} \right)}\left( {\sqrt{\frac{\Delta h_{i}}{R_{i}^{\prime}}} + \frac{T_{i0} - T_{i1}}{P_{i}}} \right)}$ from the step S5 and the step S6.1 assuming that when ${\frac{\gamma_{i}}{\alpha_{i}} = A^{-}},$ a roll gap is just in an under-lubrication state; (S6.5) calculating an under-lubrication film thickness critical value ξ_(i) ⁻ of each rolling stand according to a relation formula between the second friction coefficient u_(i) ⁻ and an oil film thickness wherein u_(i) ⁻=a_(i)+b_(i)·e^(B) ^(i) ^(·ξ) ^(i) ⁻ , and wherein ${\xi_{i}^{-} = {\frac{1}{B_{i}}\ln\frac{u_{i}^{-} - a_{i}}{b_{i}}}};$ and (S6.6) calculating a vibration determination index reference value ξ_(0i), wherein $\xi_{0i} = {\frac{\xi_{i}^{+} + \xi_{i}^{-}}{2}.}$
 3. The emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill according to claim 2, wherein the step S8 comprises the following steps: (S8.1) calculating an outlet temperature T₁ of a first rolling stand of the plurality of rolling stands, wherein ${T_{1} = {T_{1}^{r} + {\frac{1 - \left( {\varepsilon_{1}/4} \right)}{1 - \left( {\varepsilon_{1}/2} \right)} \cdot \frac{K_{1}\ln\left( \frac{1}{1 - \varepsilon_{1}} \right)}{\rho SJ}}}};$ (S8.2) enabling i=1; (S8.3) calculating a temperature T_(i,1) of a first section of strip behind an outlet of the i^(th) rolling stand, i.e. T_(i,1)=T_(i); (S8.4) enabling j=2; (S8.5) calculating a temperature T_(i,j) of a j^(th) section of strip by a relationship between a temperature of the j^(th) section and a temperature of a j−1^(th) section shown by the following equation : ${T_{i,j} = {{{- \frac{2k_{0}w_{i}^{0.264}{\exp\left( {9.45 - {0.1918C}} \right)} \times 1.163l}{v_{1i}h_{1i}\rho{Sm}}}{T_{i,{j - 1}}^{0.213}\left( {T_{i,{j - 1}} - T_{c}} \right)}} + T_{i,{j - 1}}}},$ wherein k₀ is an influence coefficient of nozzle shape and spraying angle; (S8.6) determining whether an in-equation j<m is established, if yes, enabling j=j+1, and then turning to step S8.5; otherwise, turning to step S8.7; (S8.7) obtaining a temperature T_(i,m) of a m^(th) section by iterative calculation; (S8.8) calculating an inlet temperature T_(i+1) ^(r) of an i+1^(th) rolling stand: T_(i+1) ^(r)=T_(i,m); (58.9) calculating an outlet temperature T_(i+1) of the i+1^(th) rolling stand, wherein ${T_{i + 1} = {T_{i + 1}^{r} + {\frac{1 - \left( {\varepsilon_{i + 1}/4} \right)}{1 - \left( {\varepsilon_{i + 1}/2} \right)} \cdot \frac{K_{i + 1}\ln\left( \frac{1}{1 - \varepsilon_{i + 1}} \right)}{\rho{SJ}}}}};$ (S8.10) determining whether the in-equation i<n is established, if yes, enabling i=i+1, and then turning to step S8.3; otherwise, turning to step S8.11; and (S8.11) obtaining an outlet temperature T_(i) of each rolling stand.
 4. The emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill according to claim 3, wherein the step S9 comprises the following steps: (S9.1) calculating a dynamic viscosity η_(0i) of an emulsion between a roll gap of each of the plurality of rolling stands, wherein η_(0i)=b·exp(−a·T_(i)), and in the formula, a,b are dynamic viscosity parameters of lubricating oil under an atmospheric pressure; (S9.2) calculating an oil film thickness ξ_(i) between the roll gap of each of the plurality of rolling stands, wherein the calculation formula is as follows: $\xi_{i} = {{\frac{h_{0i} + h_{1i}}{2h_{0i}} \cdot k_{c} \cdot \frac{3\theta{\eta_{0i}\left( {v_{ri} + v_{0i}} \right)}}{\alpha_{i}\left\lbrack {1 - e^{- {\theta({K\frac{T_{0i}}{h_{0i} \cdot B}})}}} \right\rbrack}} - {k_{rg} \cdot \left( {1 + K_{rs}} \right) \cdot {Ra}_{{ir}0} \cdot e^{{- B_{L}} \cdot L_{i}}}}$ in the formula, k_(rg) represents a coefficient of the strength of entrainment of lubricant by a longitudinal surface roughness of a work roll and a strip steel and is in a range of 0.09-0.15, K_(rs) represents an impression rate, wherein a ratio of transferring a surface roughness of the working roll to the strip; and (S9.3) calculating an emulsion flow rate comprehensive optimization objective function, $\left\{ \begin{matrix} {{F(X)} = {{\frac{\lambda}{n}{\sum\limits_{i = 1}^{n}\sqrt{\left( {\xi_{i} - \xi_{0i}} \right)^{2}}}} + {\left( {1 - \lambda} \right)\max{❘{\xi_{i} - \xi_{0i}}❘}}}} \\ {\xi_{i}^{-} < \xi_{i} < \xi_{i}^{+}} \end{matrix} \right.$ in the formula, X={w_(i)} is an optimization variable, and λ is a distribution coefficient.
 5. The emulsion flow optimization method for suppressing vibration of a cold continuous rolling mill according to claim 3, wherein the influence coefficient of nozzle shape and spraying angle is equal to 0.8<k₀<1.2. 